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I Forge Iron

Pictures from the Fall NEB Meet


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Here are a few pictures from the Sept. 2016 Fall Meet. 

One of the new forges for the Green Coal Tent

Bob Menard, Portland ME. NEB's V Pres demonstrating Dragons

Leigh Murrell, Colrain Mass. NEBs Treasurer with a basic Blacksmith skills (the event was hosted by his family's shop Murrell Metalsmiths)

Green Coal Tent sporting 4 of the 6 new forges, the Green Coal Tent was busy all the time, youths, ladies and folks just starting out in Blacksmithing.   

How Many Blacksmiths does it take to move a lathe from one PU Truck to another?  about 16 from what I  could tell, 4 doing the work and about a dozen of us doing the heavy looking on and giving unneeded nor wanted suggestions.  myself  I held the dog of one of the workers and watched closely,  The  dog and I did agree that the job was done well in the  end but there was some concern as to it's outcome at times.

Photos not great but haven't seen an any others.  I was only able to attend Sat. so # of Pictures are limited. 

Good time was had by all.  Watch for the Spring event. 

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I am curious about the hood design used for the sidedraft hoods on the new Green coal forge stations.  Is the "z-bend" baffle at the back setup to minimize the fly ash going up the stack?  It seems like the angled slope at the bottom and baffle section directly above would work well for that.

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I'm presuming you are right on the design.  These are all new from the spring meet and they are designed to be taken apart and loaded in NEB's trailer and hauled to meets from Portland ME.  I spoke to  the fellow who I think made the design and sells the units from a shop in NH and he said he would build and sell me a hood for my forge I'm rebuilding.  So as not to get into trouble here advertising things  I will not list him here but give me a PM and I'll give it to you  if you want.  They really seemed to work real well while I was watching.  The powers that be in NEBS I've found to be pretty sharp on these things. 

The design was the reason I took the close up of the hood. 

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It's to induce draft.  We tested a bunch of side draft hood designs and this style worked the best.  Essentially there are 2 expansion chambers, the smoke comes rocketing out of the top!  The whole forge knocks down into a flat enough bundle that it will fit in the trunk of a sedan.  We now have 6 of them in our demo trailer in the place one older forge fit.  Here is a stack of them during a fabrication workshop.

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Here are some of my pics of the meet.  

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21 minutes ago, Judson Yaggy said:

It's to induce draft.  We tested a bunch of side draft hood designs and this style worked the best.  Essentially there are 2 expansion chambers, the smoke comes rocketing out of the top!  The whole forge knocks down into a flat enough bundle that it will fit in the trunk of a sedan.  We now have 6 of them in our demo trailer in the place one older forge fit.  Here is a stack of them during a fabrication workshop.

Count Rumford would be so pleased.

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Had an interesting foray into looking at Rumford's chimney designs.  It appears that he made two basic enhancements to design of the current fireplaces of the time:

  1. Changing the inlet of the chimney to be closer to the fire and smaller to induce higher local flue velocity to aid in capture of fumes
  2. Adding mass to the fireplace to the fireplace and brining it forward of the rear wall to provide more efficient radiant heating for the room.

While I agree the "necking down" profile of the hood initially mirrors some of his design, and appreciate being introduced to it for general knowledge, I'm not sure how it specifically applies to the double enlargement indicated.  I also doubt the improved induced draft of the OP hood featured based on this double expansion, though it is hard to argue with experimental success. 

As regards increase in capture velocity, the proximity to the forge fire and relative small opening size of the standard side draft hood would appear to function well for that.  I don't see where a double expansion chamber improves that, but I could certainly be missing something.  In my experience, rapid expansions in exhaust ducting results in turbulence, which can lead to friction and lowered velocity.

Of course the ~10' high, large diameter, stack in the design features will both reduce the stack friction and lead to a very effective chimney effect exhaust.

I would expect that a similarly sized hood opening, placed in the same proximity to the fire with a smooth transition to the stack would actually suck more air.  I still think that the baffle design is more optimized to prevent hot ash and small bits of burning material from being sucked up the stack and pushed out the top by this very effective chimney effect.  Essentially I agree that it is a very good design, just not necessarily with the reason cited. 

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  • 5 years later...

Any updates (from anyone) on these questions around the utility of internal side-draft flu baffles ("expansion chambers") in the past few years since this was originally discussed?

I'm in the process of working out out a decent side-draft setup and I keep coming back to the debate on what's ideal for optimal draft. People make side-drafts out of helium tanks, barrels, fabricated sheet steel setups like these (ideal, I guess, if you have a welder...) My main question is, how necessary it is to weld in these angled baffles inside to improve the shape and draw of the flu...? I'd read somewhere that the upward back-slope at the bottom helps start the draft and the opposing forward/upward slope common in many designs that creates a "shelf" inside the box mainly just reduces blow-back from wind hitting the top of the stack up at the roof -- but I guess it's also useful at reducing ash and embers going up and out...? It seems logical that a nice open, curved path up and out would be the least turbulent and so create the best draft. Why all these Z-baffles?

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